Pregnancies complicated by preeclampsia remote from term are associated with increased morbidity for both mother and fetus. Most of the perinatal risks are related to low-birth weight (premature and small for gestational age). Additionally, the mother is at increased risk for significant cardiovascular, renal and cerebral morbidity. Recent advances in perinatal care has led to substantial improvement in maternal outcome, however, the degree of improvement in perinatal outcome has been less impressive. The purpose of the present study is to determine the clinical value of B-blocker therapy in preterm (less than 36 weeks' gestation) pregnancies complicated by mild preeclampsia. Labetalol was selected as the B-blocker of choice because of the favorable experience previously reported on its use in preeclampsia. Four hundred patients will be randomly allocated in a double blind fashion to treatment with either labetalol or placebo. Labetalol will be used to lower maternal blood pressure below 140 mm Hg systolic and below 90 mm Hg diastolic in an attempt to prevent progression to severe preeclampsia, to improve uteroplacental blood flow and prolong gestation. Patient will be enrolled into the study between 26 to 36 weeks' gestation and will remain hospitalized until delivery. Each patient will have intensive maternal and fetal evaluation of well-being through the course of the study. The clinical value of this treatment will be judged on the basis of the following outcome variables: (1) perinatal mortality; (2) immediate neonatal and subsequent infant morbidity; (3) maternal mobidity, (4) extent of maternal and neonatal hospitalization (5) monetary costs of management for both mother and infant. The interpretation of the results will include a critical analysis of risk/benefit ratios as well as the cost effectiveness of the treatment plan. It is hoped that the results of this trial can be applied clinically to improve maternal and perinatal outcome in pregnancies complicated by preeclampsia.